The need to cover substrates with sleeves made of polymeric material is well known. One particularly useful application of radially recoverable elastomeric sleeves is in the electrical cable field. Commonly assigned U.S. Pat. No. 4,045,604 to Clabburn describes a heat recoverable polymeric shedded sleeve for high voltage terminations; its disclosure is incorporated herein by reference. Heat shrink technology is used to recover and conform the sleeve disclosed in the referenced patent to the electrical termination. While heat shrink technology works very well, it requires use of a heat source, such as a torch, to cause recovery of the polymer during installation.
Another approach to installation of a radially recoverable elastomeric sleeve is described in U.S. Pat. No. 3,515,798 to Sievert, and in U.S. Pat. No. 4,389,440 to Keith. These patents describe elastomeric sleeves which are installed and maintained in radial tension or expansion upon a mandrel or core formed as a rigid, one piece spiral construction with a helical weakness or tear line integrally formed into the construction. The elastomeric sleeve is recovered and conformed to the substrate by pulling and tearing the core so that it ruptures and unravels along the tear line and thereby ceases to hold the sleeve in radial tension.
This prior approach has the drawback of complexity and expense associated with the formation of the special core. Further, the inner diameter of the assembly must be significantly greater than the diameter of the substrate to provide sufficient clearance to permit unravelling of the core. Also, because the tear line builds a structural weakness into the assembly, the assembly is somewhat susceptible to premature release and failure in the event that it is subjected to blows or other forces in transit to the worksite where it is to be installed.
A further approach for covering a substrate or workpiece with a recoverable sleeve is to be found in the disclosure of commonly assigned U.S. Pat. No. 4,070,746 to Evans, et al. With the approach described therein a sleeve was bonded in radially expanded or extended state to an outer restraint. The bond between the restraint and the sleeve was sufficiently strong to retain the sleeve in its expanded condition under ordinary conditions of storage and handling, and was broken for installation upon the substrate by application of a suitable bond-attacking solvent. While the approach described in this patent works quite well, it has the drawback of added cost, and the need for providing and applying the solvent at the installation worksite.
Another approach for installing a sleeve upon an electrical termination, for example, is disclosed in U.S. Pat. No. 4,685,189 to Palmquist et al. The approach of this patent is to provide a pliable sleeve which is turned inside out and lubricated when fitted upon the substrate such that the sleeve rolls over itself as it is positioned longitudinally over the previously prepared substrate, e.g. a cable end. However, if weather sheds are needed for high voltage terminations, those sheds must be separate from the sleeve and fitted over the sleeve after installation.
A double walled sleeve which is also installed by revolving over a substrate by shear between the two walls is described in the commonly assigned U.S. Pat. No. 4,868,967 to Holt et al., the disclosure of which is hereby incorporated by reference. While this rollover approach is successful for the intended purpose of providing electrical and/or environmental protection high voltage weather sheds may be difficult to form integrally with the sleeve.
Thus, a heretofore unsolved problem has remained for an improved recoverable sleeve which may be made and supplied at low cost and which may be easily applied or installed by the craftsman without need for any special tools, i.e. tools not normally available to the craftsperson in the field.